Many industries need to detect and quantify the concentration and level of biological material in a sample. For example, the determination of bacterial concentration in food and water is an essential part of food and water quality testing. EPA regulations require that no coliforms, such as Escherichia coli, be present in potable water. The “presence/absence” format of a testing medium, such as Colilert® chemical mixture (IDEXX Laboratories, Me.), which is used as a testing medium for Escherichia coli and all coliform bacteria, is very useful in making this determination.
However, there are areas where the quantification, not just the detection, of microorganism concentration is important. Examples of such areas include waste water, incoming water in water purification systems, surface water, and food testing.